Lithography/dry etch processes often yield critical dimension (CD) or feature size non-uniformity across a substrate (e.g., a wafer). Being able to characterize such non-uniformity is critical for process control in semiconductor manufacturing, as it translates to wafer yield and final device performance. There are a variety of metrology and/or inspection tools that can be used to analyze samples (e.g., wafers or other substrates) to determine feedback or feedforward data for advanced process control (APC) loops. SEM tools have good sensitivity to offer in any inspection or metrology application, but SEM tools tend to be much slower than optical tools. Accordingly, improvements are needed for SEM-based inspection and metrology systems.